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P0178: Fuel Composition Sensor Circuit Low

Severity
Medium
System
Fuel and Air Metering

What Does P0178 Mean?

P0178 is a diagnostic trouble code indicating: Fuel Composition Sensor Circuit Low. This code relates to the fuel and air metering system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of P0178

Common Causes

Frequently Asked Questions

What does P0178 mean?
P0178 indicates: Fuel Composition Sensor Circuit Low. The vehicle's computer has detected that the Fuel Composition Sensor is not operating within its expected parameters and stored this diagnostic trouble code.
Can I drive with code P0178?
You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P0178 for extended periods may cause additional problems.
How much does it cost to fix P0178?
Repair costs for P0178 typically range from $20 to $300, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

  • 🔧 Repair broken wire or restore ground in Fuel Composition Sensor circuit
  • 🔧 Clean and secure Fuel Composition Sensor connector and ground points
  • 🔧 Replace failed Fuel Composition Sensor
  1. 1
    Find your vehicle above

    Click your make and model for real owner reports and common causes specific to your vehicle.

  2. 2
    Check for recalls

    Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.

  3. 3
    Get a professional diagnosis

    A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

Related Codes

P0100 Mass or Volume Air Flow Sensor A Circuit P0101 Mass or Volume Air Flow Sensor A Circuit Range/Performance P0102 Mass or Volume Air Flow Sensor A Circuit Low P0103 Mass Air Flow Circuit High Input P0104 Mass or Volume Air Flow Sensor A Circuit Intermittent P0105 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit P0106 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Range/Performance P0107 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Low P0108 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit High P0109 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent